The present invention relates to a track-traveling four-wheel vehicle suitably adapted to serve as an amusement four-wheel vehicles which travels along a track having a pair of rails by means of pedalling or power.
In general, track-traveling vehicles used in an amusement ride in an amusement park travel along a track comprising a combination of straight and curved paths. The track is conventionally constituted by a single rail to allow free travel along a curved path. Furthermore, a saddle-type vehicle as described in Japanese Utility Model Publication No. 11806-1982 or a suspension-type vehicle have been proposed which travel along a single rail.
However, in order to ensure the safety of vehicles traveling along a single rail, the saddle-type vehicle requires a mechanism for lowering the center of gravity of the vehicle body; and the suspension-type vehicle requires various types of complicated safety mechanisms. Therefore, conventional amusement vehicles have serious mechanical design problems. Even if a safety mechanism is provided on a conventional vehicle, the vehicle body is heavy. As a result, easy travel is difficult when such a vehicle is used as a pedal-driven vehicle.
One proposal is a double rail track that is used in place of the single rail track, and a four-wheel vehicle that is employed to travel along the double rail track safely and comfortably. In this case, the four-wheel vehicle must travel along a curved track having two rails. Therefore, all four wheels, or either the front or rear wheels of the vehicle must move about a swingable shaft so as to allow smooth travel of the vehicle along the two curved rails. In four-wheel vehicles of this type, the rear axle is immovably fixed on the vehicle body, and the front axle is swingably mounted on a center plate extending from the bottom of the vehicle body through a center plate support. When the vehicle approaches a curve, the front wheels are forcibly guided along the curved rails whereupon the front axle swings, allowing travel on a curved surface. However, such a four-wheel vehicle traveling along the two rails cannot handle a sharp curve. Therefore, it is impossible to effectively utilize a narrow amusement park space as an amusement ride area through use of sharp curves, nor is it possible to provide the thrills associated with sharp curves.
A four-wheel vehicle suitable for curved travel has also been proposed wherein both the front and rear wheels swing. This four-wheel vehicle has a small radius of rotation at a curve or a corner. Therefore, a narrow amusement park area can be effectively utilized, and greater thrills can be provided. Furthermore, since the vehicle can smoothly turn the corner, only a small friction resistance between the wheels and the rails occurs. As a result, even if the vehicle is driven by pedalling, the passenger (driver) will not tire easily. However, since the rear wheels are swingable, it is very difficult to transmit power thereto, resulting in a complex driving force transmission mechanism. For that reason, the above-mentioned vehicle is not suitable as an amusement ride vehicle. The rotational force is transmitted from a large sprocket of a pedal mechanism to a small sprocket of the rear axle through a chain. In this case, the chain must remain in a single plane to avoid chain removal. Therefore, it is very difficult to swing the rear axle in accordance with conventional techniques.
In a track of such track-traveling amusement rides, since a flat course becomes monotonous, a winding track having ups and downs is preferred. In other words, up and down inclines and switch backs are formed along the track. Furthermore, a drive mechanism is used to pull the vehicle up to the top of an incline so as to allow the vehicle to plunge downward by its own weight. A vehicle for traveling along such a track generally has a brake unit, so that the passenger can operate the brake to adjust the speed of or stop the vehicle. However, if the passenger operates the brake during an interval wherein the vehicle is adapted to climb up the next hill by through inertia or by a combination of inertia and a pedalling force, the vehicle cannot climb the hill, and stops in a valley. Even worse, the subsequent vehicle may collide with the vehicle stopped in the valley. Furthermore, when the passenger operates the brake during intervals wherein maintenance personnel are operating a drive mechanism to pull the vehicle up to the top of a hill or to guide the vehicle to a predetermined platform position, the drive mechanism break, resulting in a dangerous situation.